Add date filter token to dashboard

What does this MR do and why?

Feature flag was not being passed to this page, which meant feature was missing and we got a 'injected value is undefined' warning in the console.

Currently the data attribute is added in ruby in common_issues_list_data (only for issue list page), so added it to the dashboard data as well.

before	after

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable feature

   Feature.enable(:issue_date_filter)

2. Visit issue dashboard page
3. Filter issues by "created date" and "closed date"

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.